1. Field of the Invention
The present invention relates to a bubble-jet type ink-jet printhead.
More particularly, the present invention relates to an ink-jet printhead having a hemispherical ink chamber and a method for manufacturing the same.
2. Description of the Related Art
Ink-jet printheads are devices for printing a predetermined image by ejecting small droplets of printing ink at desired positions on a recording sheet. Ink ejection mechanisms of an ink-jet printer are generally categorized into two different types: an electro-thermal transducer type (bubble-jet type), in which a heat source is employed to form a bubble in ink causing an ink droplet to be ejected, and an electromechanical transducer type, in which a piezoelectric crystal bends to change the volume of ink causing ink droplets to be expelled.
FIGS. 1A and 1B are diagrams illustrating a conventional bubble-jet type ink-jet printhead. Specifically, FIG. 1A is a perspective view illustrating the structure of an ink ejector as disclosed in U.S. Pat. No. 4,882,595. FIG. 1B illustrates a cross-sectional view of the ejection of an ink droplet in the conventional ink ejector.
The conventional bubble-jet type ink-jet printhead shown in FIGS. 1A and 1B includes a substrate 10, a barrier wall 12 formed on the substrate 10 to form an ink chamber 13 for containing ink 19, a heater 14 installed in the ink chamber 13, and a nozzle plate 11 having a nozzle 16 for ejecting an ink droplet 19xe2x80x2. The ink 19 is supplied to the ink chamber 13 through an ink channel 15, and the ink 19 fills the nozzle 16 connected to the ink chamber 13 by capillary action. In a printhead of the current configuration, if current is applied to the heater 14 to generate heat, a bubble 18 is generated in the ink 19 filling the ink chamber 13 and continues to expand. Due to the expansion of the bubble 18, pressure is applied to the ink 19 within the ink chamber 13, and thus the ink droplet 19xe2x80x2 is ejected through the nozzle 16. Next, ink 19 is supplied through the ink channel 15 to refill the ink chamber 13.
There are multiple factors and parameters to consider in making an ink-jet printhead having a bubble-jet type ink ejector. First, it should be simple to manufacture, have a low manufacturing cost, and be capable of being mass-produced. Second, in order to produce high quality color images, the formation of minute, undesirable satellite ink droplets that usually trail an ejected main ink droplet must be avoided. Third, when ink is ejected from one nozzle or when ink refills an ink chamber after ink ejection, cross-talk with adjacent nozzles, from which no ink is ejected, must be avoided. To this end, a back flow of ink in a direction opposite to the direction ink is ejected from a nozzle must be prevented during ink ejection. Fourth, for high-speed printing, a cycle beginning with ink ejection and ending with ink refill in the ink channel must be carried out in as short a period of time as possible. In other words, an ink-jet printhead must have a high driving frequency.
The above requirements, however, tend to conflict with one another. Furthermore, the performance of an ink-jet printhead is closely associated with and affected by the structure and design of an ink chamber, an ink channel, and a heater, as well as by the type of formation and expansion of bubbles, and the relative size of each component.
In an effort to overcome problems related to the above requirements, various ink-jet printheads having different structures have already been suggested in U.S. Pat. Nos. 4,882,595; 4,339,762; 5,760,804; 4,847,630; 5,850,241; European Patent No. 317,171; and Fan-gang Tseng, Chang-jin Kim, and Chih-ming Ho, xe2x80x9cA Novel Microinjector with Virtual Chamber,xe2x80x9d IEEE MEMS, pp. 57-62, 1998. However, ink-jet printheads proposed in the above-mentioned patents and publication may satisfy some of the aforementioned requirements but do not completely provide an improved ink-jet printing approach.
In an effort to solve the above-described problems, it is a feature of an embodiment of the present invention to provide an ink-jet printhead having a hemispherical chamber, which is capable of effectively cooling heat generated by a heater, and a method for manufacturing the same.
Accordingly, an embodiment of the present invention provides a method for manufacturing an ink-jet printhead having a hemispherical chamber. The method includes forming a ring-shaped groove for forming a nozzle guide at the surface of a substrate, forming a nozzle plate and a nozzle guide having a multi-layered structure and including a thermally conductive layer formed at the surface of the substrate, forming a heater on the nozzle plate, forming a manifold for supplying ink by etching the substrate, forming an electrode on the nozzle plate to be electrically connected to the heater, forming a nozzle having almost the same diameter as the nozzle guide by etching the nozzle plate inside the heater, forming an ink chamber in a substantially hemispherical shape by etching the substrate exposed through the nozzle, and forming an ink channel for supplying ink from the manifold to the ink chamber by etching the substrate.
Here, forming the nozzle plate and the nozzle guide preferably includes forming a first insulating layer at the surface of the substrate and the inner surfaces of the ring-shaped groove, forming the thermally conductive layer by depositing polysilicon on the first insulating layer and simultaneously forming the nozzle guide by filling the polysilicon in the ring-shaped groove, and forming a second insulating layer on the thermally conductive layer.
According to the present invention, since an ink chamber, an ink channel, and a manifold for supplying ink are integrally formed in a substrate into one body and a nozzle plate, a heater, and a nozzle guide are also integrally formed on the substrate into one body, the manufacture of an ink-jet printhead having a structure according to the present invention is simplified, and thus mass production of the printhead is facilitated.